High volume purification of contaminated liquids, such as sewage water, waste water or saline water, is a major technical and economical challenge. This challenge becomes important due to the current shortage of fresh water supplies for consumption or agriculture. Several conventional methods have been proposed for providing purified liquids, such as mechanical methods or thermal methods. The mechanical methods, such as reverse osmosis, require the use of membranes or filters to separate a liquid from its foreign objects. The foreign objects are concentrated in a drain liquid that needs to be further treated or that is rejected to the environment. This rejection of foreign objects to the environment harms the environment.
In thermal methods, such as a multi-stage flash evaporation, a multi-effect distillation and a mechanical vapor compression, the contaminated liquid is heated and re-condensed while its foreign objects are separated during the phase transitions of the liquid. Even though thermal methods typically produce liquid of high purity these methods require large amount of energy. In particular, such systems require mechanical energy to pump the contaminated liquid into the system or to maintain certain pressure gradients within the system. The mechanical energy required is generally more expensive than thermal energy. Moreover, these systems have a complex configuration and, thus, have very high initial costs of construction and initial operation. Therefore, the use is more limited to large scale municipal installations. As in mechanical methods, thermal systems also produce a large amount of drain liquid including the concentrated foreign objects, such as high salinity water. These concentrated foreign objects are often rejected to the environment and, therefore, may be detrimental to the environment.
Therefore, there is a need for a liquid purification method and system, that have manageable initial costs, enable an energy efficient operation, and that are safe for the environment.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.